Work-clamp for sewing machines



Sept. 15, 1931. E. B. ALLEN WORK CLAMP FOR SEWING MACHINES Filed Nov.

15, 1928 5 Sheets-Sheet 1 llll llllllllllll ll Sept. 15 1931. E. B. ALLEN WORK CLAMP FOR SEWING MACHINES Filed Nov. 15. 1928 3 Sheets-Sheet -2 p 15, 1 31- E. B. ALLEN 1,823,522

WORK CLA-MPEOR SEWING MACHINES Filed Nov. 15, 1928 s Shee'ts-Sheet :5

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WMWAA Patented Sept. 15,

Un ts!) STATES PATENT OFFICE EDVARD B. ALLEN, F NEWTOWN, CONNECTICUT, ASSIGNOR TO THE'SINGER MANU- FACTURING COMPANY, OF ELIZABETH, NEW JERSEY, A CORPORATION OF NEW JERSEY wonK-cLAMe son SEWING MACHINES Application filed November 15, 1928. Serial No. 319,476.

This invention relates more particularly to buttonhole sewing machines and has for one of its objects to provide a work-clamp for such machines which is self-adapting to work of any thickness or texture within wide limits. Another object of the invention 1s to provide a work-clamp, the upper clamping feet of which have a uniformly high lift above the work-suppor-.ing plates for "all m classes of work, whether thick or thin, hard or soft. A further object of the invention is to provide for the independent self-adaptation of the right and left clamping sections of the work-clamp to work of different thicknesses under the respective clamping feet.

Still further, the invention has for an object to provide a work-clamp which automatically accommodates itself to all classes and thicknesses of work, either soft and spongy. or relatively hard and unyielding; a proper clamping pressure being applied to the work in all cases.

To the attainment of the ends in view the clamp-closing mechanism is provided with work-governed means for controlling the amount of closing movement imparted to the work-clamping elements; the amount of closing movement being increased for thin work and decreased for thick work. The governing means preferably comprises a feeler element which is automatically moved, in the initial stage of the clamp-closing movement, until it gages the thickness and compressibility of the work, whereupon. the feeling movement of the fecler ceases and the closing of the clamp is completed by suitable pressure-applying means. Preferably, the fe e l er element is made in the form of a travelling wedge which is advanced in the initial stage of the clamp-closing operation. until it encounters the resistance caused by engagement of its respective clamping foot with the work, thus acting through the clamping foot and its carrier lever.

The invention will be better understood by reference to the accompanying drawings in which Fig. 1 is a plan View of a bnttonhole sewing machine work-clamp embodying the M5 invention. Fig. 2 is an inner side elevation of one of the clamping sections of the workclamp. Fig. 3 is an outer side elevation of the work-clamplng section shown in Fig. 2.

Fig. 4 is asection on the line 4+4, Fig. 2.

9 is a perspective view of the fulcrum support for the clamp-closing lever. Fig. 10 is a view similar to Fig. 2, showing the operation of the clamp on thin work. Fig. 11 is a similar view showing the operation of the clamp on thick work. Fig. 12 is an elevation of the feeler-wedge of Fig. 2, and Fig. 13 shows a modified form of feeler-wedge construction.

The invention is shown as embodied in the work-clamp of a buttonhole sewing machine having substantially the constructive features disclosed in the U. S. patent to E. B. Allen, No. 15,324, reissued Apr. 4, 1922. The workclamp of a buttonhole sewing machine of this type comprises separable clamping sections A and B in right and left arrangement, meeting along the center line C. The clamp-sections A,"B are pivotally mounted at d, d for spreading movements on the cross slide-plate e which, in turn, is mounted for lateral movement on the longitudinal slide-frame. comprising the side bars f and tie-rod g.

Throughsuitable movements imparted to the cross slide-plate e and longitudinal slideframe f, the work-clamp is so moved as to place the buttonho-le stitches in the desired arrangement around the buttonhole. The clamp-sections A, B are substantially identical, except for the right-hand and left-hand arrangement of their component parts.

Each work-clamp section comprises a worksupporting plate 1 to the rear end of which is secured a fulcrum-block 2 between the side Journaled in the side bars 3 are the alined I clamp-closing rock-shaft sections 9, 9', the inner ends'of which are connected together for equal turning movements by the usual interengaging arms 10, the arm 10 being formed at its free end with a fork 11 to embrace the pin 11 at the free end of the arm 10.

Fixed to the rock-shaft sections 9, 9 are the clamp pressure-applying cams 12 and clownwardly extending arms 13; the latter passing through slots 14 in the clamp-levers 7. Slidably mounted on the clamp-levers '7 are the feeler-elements or wedges 15, the tapered front ends of which are slotted at 16 to clear the arms 13. From the bottom faces of the feeler-wedges project the lugs 18 which extend downwardly through the slots 14 in the clamplevers 7 and are connected by springs 19 to the arms 13.

The clamp-levers 7 are yieldingly elevated to a constant or uniformly high open position by springs 20 secured at their forward ends to the inner faces of the inner side bars 3 of the fulcrum-blocks 2 by screws 21. The rearward ends of the springs 20 are extended laterally through clearance holes 22 in the side bars 3 into under-lapping engagement with the clamp-levers 7.

The clamps are closed by a rocking movement of the connected rock-shaft sections 9, 9. This rocking movement is imparted to the shaft-sections, either by the manually operated arm 23 (Fig. 1) or the automatically operated arm 24 fixed to the rock-shaft section 9; the arm 24 receivinga down-movement from a lever 24 of the buttonhole sewing machine, as described in said Allen reissued patent.

. When the clamps are closed, as shown in dotted lines, Fig. 3, they are held closed by engagement of the front end 25 of the spring-pressed latch 25 with the arm 26 fixed to the rock-shaft section 9. When the latch is tripped, either manually or by suitable mechanism of the machine, the clamps spring open; the open position of the parts being, determined by engagement of the arm 26 with the shoulder 25 of the latch 25.

When the clamps are open (see Fig. 10) the cams 12 engage the forward end-portions of the tapered faces 27 of the feeler-wedges 15. During the first part of the rocking ing feet '8 encounter the resistance of the work, whereupon the advance of the feelerwedges is arrested since the force required,

to advance such wedges after the clamp feet lightly engage the work is quite considerable and is in excess of the force transmitted by the springs 19. The cams 12 and wedges 15 each generate clamp-closing motion in the clamp-levers 7 and, being in series relation,

' their effects are additive.

95' motion, so far, may be considered asthe initial or work-gaging stage of the,

clamp-closing operation, and it will be seen that the advance of the feeler-wedges 15 is governed by the thickness of the work; the thinner the work, the greater the advance of the wedges. When the advance of the wedges is arrested by the resistance of the work, the continued down-motion of the cams 12 applies pressure to the clamp-levers 7 and causes the feet 8 to securely grip the work upon the plates 1. The resistance required to be encountered by the clamping feet 8, to stop the advance of the wedges 15, while relatively light, is suflicient to cause the feet 8 to lightly or initially compress work of a soft or spongy texture and hence the wedges 15 gage the texture of the work, as well as its thickness, in determining the end of the initial stage of the clamp-closing operation and the beginning of the second or workcompressing stage.

When the clamps are opened, the springs 19 operate as links to push the wedges 15 back to their initial retracted positions permitt-ing the clamplevers 7 to always rise to the same high position regardless of the thickness of the work. The springs 19 are strong enough in tension to hold the wedges 15 against any possible tendency toward backward slipping during the clamp-closing operation. Furthermore the wedges 15 act independently of one another, each operating to gage the work under its respective clamping foot 8. Hence, the clamps will satisfactorily grip work varying in thickness under the respective feet 8, without necessitating the exertion of an abnormally heavy pressure upon one foot to obtain a secure grip of the other foot upon the work. Thus, the feeler elements 15 serve to gage the thickness and compressibility of the work during the clamp-closing operation and automatically determine the final pressure applied by the cams 12. It will be understood that the advance of the feeler-elements 15 is governed by the thickness of the work and that they control the extents to which the respective clamp-levers 7 are depressed by the cams 12.

By suitably inclining the faces 27 of the wedges 15 at different portions of their ef-- fective lengths, variations in the-final clamping pressures may be obtained for work of different thicknesses. In the present instance the forward portions of the faces 27 of the wedges 15 are inclined at an angle of about 22 to the bases and the rearward portions at an angle of about 19. In the particular embodiment of the invention illustrated, these inclinations are found to give suitable clamping pressures for the average runs of thin and thick work for buttonhole sewing ma chines. The inclined faces may be continuously. curved from front to rear as shown at 27, Fig. 13, or given any desired shape or curve to produce the require action of the clamp.

While the invention is shown and described as used in a work-clamp for a buttonhole sewing machine, it is not to be understood as limited to such use. Nor is the invention limited to the specific form and arrangement of parts herein described, as it is obviously susceptible of embodiment in various other specific forms, within the spirit and scope of the invention.

Having thus set forth the nature of the invention, what I claim herein is 1. A work-clamp including a work-clampin g element having a constant open position and a variable closed position, clamp-closln means, and encompressible means associated with the clamp-closing means for automatically determining the closed position of the work-clamping element in accordance with the thickness of the Work.

2. A work-clamp having a work-clamping element, and clamp-closing means including an automatically adjustable incompressible element governed by the thickness of the work tor regulating the amount of positive movement imparted to the work-clamping element by the stamp-closing means.

3. A Work-clamp including a work-clamping element and clamp-closing means having a two-stage closing movement viz., an 1n1t1al stage and a work-compressing stage, and means governed by the thickness of the work and having a compensating movement 1n the initial stage of the clamp-closing operation for determining the end of the initial stage and the beginning of the work-compensating stage.

A. A work-clamp including a work-clamping element having a two-stage closing movement via, an initial stage and a work-com- Jressing stage, and clamp-closing means including a travelling feeler-wedge generating motion in the work-clamping element in the initial stage of its closing movement, and a pressure applying cam for completing the closing movement.

5. A Work-clamp having a work-clamping element, and clamp-closing means including a pressure-applying element and an incompressible teeler-element interposed between the pressure-applying element and the work-clamping element and automatically movable relative to the latter during the clamp-closing operation.

6. A work-clamp having a work-clamping element movable between open and closed positions, and clamp-closing mechanism including pressure-applying member and a Wedge intermediate the pressure-applying member and the work-clamping element, said clampclosing mechanism also including means for imparting a feeling movement to the wedge.

7. A work-clamp having a movable Workclamping member, clamp-closing means including a pressure-applying member, and a feeler-wedge disposed intermediate the pressure-applying member and the work-clamp ing member and automatically movable transversely of the direction in which the clampclosingpressure is applied by the pressureapplying member.

8. A Work-clamp having a. pair of inde ing element, clamp-closing means includinga plurality of clamp-closing elements acting in series relation to each generate a part of the total closing motion imparted to the work-clamping element, and means permitting the arrest of the clamp-closing motion of one of said clamp-closing elements during a continuance of the motion of another clampclosing element.

11; A work-clamp having awork-clamping lever,'a clamp-closing rock-shaft, a cam on said rock-shaft, a feeler-wedge slidable lengthwise of said work-clamping lever intermediate the latter and said cam, and yielding means connected to said rock-shaft for sliding said wedge.

r 12. A work-clamp having a work-supporting plate, a work-clamping lever, a clampclosing rock-shaft, a cam on said rock-shaft for depressing said lever, a wedge interposed between said cam. and lever, an arm on said rock-shaft, and a spring-connection between said arm and wedge.

13. A work-clamp having a work-clamping i element, a clamp-closing element, and clamppressure-regulating means having a variable position of engagement with said clampclosing element and automatically governed as to its position of engagement by the thickness of the work.

14. A work-clamp having a work-clamping element, a clamp-closing element, and clamp-pressure-regulating means having a variable movement of interposition between the work-clamping element and clamp-closing element, and governed in the extent of its movement of interposition by the thickness of the work.

15. A Work-clamp having a work-clamping element, clamp-closing means, and an incompressible clamp pressure regulator movable relative to the clamp-closing means I element.

and governed by the thickness of the work for modifying the action of the clamp-closing means upon the work-clamping element.

16. A Work-clamp having a Work-clamping element, a clamp-closing element, and an unyielding Work-governed element variably aplied relative to the clamp-closing element to vary its action upon the worbclampin'g element.

17. A Work-clamp having a work-clamping element, a clamp-closing element, and a Work-governed Wedge for varying the action of the clamp-closing element upon the Workclamping element.

18. A Work-clamp having a Work-clamping element, a clam-closing element, and an unyielding Work-governed element variably interposed between the clamp-closing element and the Work-clamping element.

19. A Work-clamp having a Work-clamping element, a clamp-closing element, and a Wedge movable by and cooperating With the clamp-closing element to vary its action upon the Work-clamping element.

20. A Work-clamp having a Work-clamping element, a clamp-closing element, and

Work-governed means movable-bodily relative to said elements to Vary the action of the clamp-closing element upon the Workclamping element.

21. A work-clamp having a Work-clamping element, a clamp-closing element, and a Work-governed clamp pressure regulating element having an operative movement relative to said Work-clamping and clamp-closing elements which varies inversely With the thickness of the Work. I r

22. A Work-clamp having a Work-clamping element, a clamp-closing element, and a work-governed clamp-pressure regulating element movable relative to said elements prior to engagement of the Work-clamping element with the Work.

23. A Work-clamp having a work-clamping element, a clamp-closing element, and Work-governed means interposed between said elements and bodily shiftable relatively thereto for varying the action of the clampclosing element upon the Work-clamping In testimony WhereofpI'haVe signed my name to this specification. g V EDWARD B. ALLEN. 

